Impregnating pitch and process and product utilizing it



roamed Mar. 10, 1936 UNITED STATES IMPREGNATING PITCH AND PROCESS ANDPRODUCT UTILIZING I'I.

Ira Derby, Indianapolis, Ind.,- assignor to PER! C. Reilly, IIIMDQIIS,Ind.

No Drawing.

3 Claims.

My invention relates to the impregnation of cellulosic fibrous materialand products,- such as paper, cloth, wood-pulp sheets and-conduit,roofing paper, and fibrous insulating materials,.as.

' well as wood itself, with water-proofing compounds ofipitchycharacter, such as coal-tar pitch, water-gas-ta.r pitch, and/orpetroleum pitch, and various mixtures of pitches; to the process ofimpregnation involved; to the special impregnating materials used; andto the final impregnated materials, more especially impregnated conduit.v V

It is the object of my'invention to increase the absorption if suchpitchy material into the fibrous materials to be impregnated, so that. agreater amount of the pitchy material may betaken into the pores of thef fibrous material; toserve the o multiple purpose of increasing thewater-imperviousness, of increasing both the dielectricstrength 29 thestrength, .of decreasing the 1owermrbr dielectric'strength underwater-absorption conditions, and of improving the appearance of thetreated material.

This invention is based on the discovery that the absorption of pitch bycellulosic fibrous ma- 'terlals maybem'arkediy increased in rate andextent, and "water-imperviousness promoted, by the coniointfuse with thepitch. to be absorbed of phenolic tar-acid. By phenolic tar-acid I meansuch phenolic bodiesas those which normally occur in coal-tar, and theiranalogs, homologs, and isomerldes, lwhether o1 synthetic or otherorigin. That is, tar-Y-acids which I use in any particu- 5 sources thancoa1- tar.-

ong the phenolictar-acids which are suit able, either-in thecrude or therefined state, are

acid oil) I 3-- ar ms rl e d 4 Qrtho-cresol 5.]Para-bresol A 6.Meta-cresolfl= i e J. 1, "tilxylenols t Q 9 .iHig h-boilingjtar-acids10.' Low-teniperature tar-acids i V 11 Qrtho-phenyl phenol 1 12.Alpha-naphthol la Beta-naphthol 4 14. Pymr ws i l6. of oils with the taracids or. with mixtures of tar-acids, whether the oil is a tar oil orsome other kind ofoilsuch lar case may actuallybe. derived from,other iare desirably dried before impregnation.

2. variously composite tar- 7. Mixtures of cresols, asof metaci'esol andApplication December 18, 1931, Serial No. 581,987

In carrying out my invention I may use any suitable impregnating pitch;and I use with it a phenolic tar-acid material such as referred toabove. The pitch vI prefer is a water-gas-tar pitch which melts betweenand C. The 5 additional material may be mixed with the pitch, and-themixture applied as a unit in a single impregnating process; or theadditional material may be preliminarily applied to the fibrous materialto be impregnated, and the pitchy materlal applied subsequently. Thetemperature used for impregnation should be sufiiciently high to makethe impregnating materials flow fairly freely, and should be as highasconveniently pos- 'sible withoutcauslng deterioration of either thetreated or the treating materials. In practice,

the impregnating temperature is well 'over' C., but ,usually under, 200C.; and for most pitches a satisfactory. impregnating temperature isabout .to (2. The impregnation may be made by simply/soaking the fibrousmaterial for a suitable time, or-may be made under pressure to obtaingreater penetrationin shortened time.

I will describe my invention particularlywith 25 reference to theimpregnation of electric conduits, of the type made of news-printpaper-pulp or wood-pulp; and from that it will be clearly apparent howmy invention is used on other types of cellulosic fibrous material.

These conduits are commonly from about 2 to 8 inches across, in lengthof from 3 to 12 feet, with walls of from y inchto inch in thickness, orthereabouts. After 'being formed; these conduits For many years it hasbeen the custom; to im-' pregnate these conduits with pitch, byimmersing themin a pitch bathfor 7 or8 hours and then I allowing them tocool, with the pitch. bath m'airitained at a temperature of about 150 to185? (140+ The normal mean absorption of pitch has been in thenemhborhood of 1* i0%"to' %[of1the weight of the untreated conduit; Aconduit so treatedis fairly water-impervious, but, not much was is to bedesired. 'Whentested, forflli water absorption by being immei sed inwater at 21 C. for 48 hours the mean absorp ion of water I,

is ordinarily found to be from 5,% to 15% of the weight of thepitch-treated conduit. When such absorption of water occurs in aconduitin actual use, the resultant lowering of dielectric strength 9 isvery pronounced. ordinarily to about 40%, to 60%.

Instead of using the sim a pitcnihat has heretofore been used forimpregnation, I use, i such pitch together with some one or" more of,

the phenolic tar-acids above referred .to as the impregnating material.The quantity. of taracid used may be relatively small in on to thequantity of. pitch. In most instmces it-is' suflicient to use as littleas from 1% to 3% taracid as reckoned on the weight of the pitch used;although in some instances it is desirable to use more tar-acid thanthat for best results, up to 8% or 10% in the case of beta-naphthol forinstance, while in others it is possible to get good results with less,for instance as little as 0.2% in the case of crude composite tar-acidsfrom taracid oil. In any case, it is desirable to use enough of thephenolic tar-acid to cause an increase in the total quantity of pitchwhich will be absor Bed by the cellulosic fibrous material (the conduit)in a given time under specified conditions.

It is found that with conduit thus impregnated, so that a greater amountof pitch is absorbed, the water-imperviousness of the conduit ismarkedly increased over that of previously known conduits, theproportionate increase varying with the nature and amount of thetar-acids used. The pitch absorption by the use of the tar-acids may beincreased by as much as 40% or 50% in some instances, over that of theunmodified pitch; and the mean water absorption of the conduit soimpregnated with the modified pitch under the test for absorption byimmersion in water for 48 hours at 21 C., may easily be reduced to below3% of the weight of the treated conduit, and in most cases below 1%thereof. In many instances, with this water-absorption test, we havebeen able to get a mean absorption below 0.5% of the weight of thetreated conduit. Thus the lowering of water-absorption under givenconditions is of the order of 40% to 90%, and even more in someinstances, as compared to previous commercial pitch-treated conduits.

The following table shows some results that were actually obtained bythe use of water-gastar pitch melting between 50 C. and 80 C. and

containing the indicated percentages of various phenolic tar-acidsPercentage Percentage absorption water sbso The material added to thepitch of mm on in ma hours at 21 0.

Percent Percent 0.5 crude composite tar-acids 228 0. 32 l. crudecomposite tar-acids; 251 0. 27 2. a crude composite tar-acids; 271 0. 15

' 22! 0. 2i 2% 0. 40 246 0. B 242 0. 00 248 0. 05 henol 228 0. 7

2. undo com to tau-acids 1g i ttaa'anuazi (I'll ecom treatment) m4 1. 1

aoeaees The treatments shown in the above table, except the last two,were all for 7% hours, the first '7 hours at 160 C. and the last hour at182 C.; which conforms to standard practice in impregnating conduits.The last two lines of the table, however, show that in my process it ispossible to use a. shortenedtreatment, for there the treatments were fortotals of only 4% hours and 1 hour respectively, at 160 C. I

Thus a marked increase in the amount of pitch absorbed, and/or a greatsaving in impregnating time, may be obtained in impregnating processesby the use of my modified pitch. The saving in impregnating time isespecially marked when the impregnation is carried only to the extent ofprevious iml s ations.

In the examples shown in the table given above the treatment is made bymixing the pitch and the indicated phenolic tar-acid, andimpregnating'the conduit in a single impregnating treatment. However, Ihave also gotten good results by treating the conduit first with thephenolic tar-acid and subsequently impregnating with the pitch. In thelatter case, the treatment of the conduit with the tar-acid may be inany convenient way, as by dipping, brushing, or spraying, using eitherthe tar-acid alone, the tar-acid dissolved in a solvent (such asbenzol'), or the tar-acid made into an emulsion (even with water). Theamount of tar-acid used is so small in comparison to the pitch that whenit is applied preliminarily it is not in sumcient amount to make acomplete impregnation by itself of the treated material; but it somehowcombines with and modifies the subsequently applied pitch so that thepenetration of the latter is facilitated.

With the impregnation by modified pitch as above outlined; I not onlyget an increase in the .amount of absorption of the treating material,

and a decreased amount of water-absorption under similar water-exposureconditions, but I also get an increase in the dielectric strength of theconduit, an increased mechanical strength, a decrease in theproportionate lowering in dielectric strength under given water-exposureconditions, and an improved appearance. The surface of the conduit whichhas been treated with my modified pitch is usually a uniform lustrousblack on both inner and outer surfaces, with a thin but even outer sealcoating instead of the thick irregular outer coating seen in thoseprevious conduits in which it has been sought to obtain a seal coat. Ifpreferred, a dull surface may be obtained, for instance if phenol ormeta-cresol is used as the pitch-modifying agent.

Although I have primarily described my invention for electric conduit,in which telephone or telegraph or similar conductors are placed, myinvention is applicable to various other cellulosic fibrous materials.For instance, fabric insulation can be impregnated in the mannerdescribed above for conduit. 80 can wood; although it is desirable todry the wood first, so that penetration into the wood may not beinterfered with by moisture in the wood-pores. The wood that is treatedmay have been previously creosoted if desired. I have also used the sameimpregnating materials and processes for vegetable-fiber plates orsheets. such as various wall-boards, fibrousbase tiles, etc. These aremerely examples of the materials to which my invention is applicable.

I claim as my invention: v 1. The process of treating relativelyinflexible prefabricated cellulosic fibrous material, which consists inimpregnating it with water-gas-tar pitch containing from 0.2% to 10.0%of phenolic tar-acid.

2. An impregnating pitch of the class consisting of coal-tar pitch andwater-gas-tar pitch, containing between 0.2% and 10.0% phenolic taracid,for impregnating relatively inflexible prefabricated cellulosic fibrousmaterial such as conduit.

3. An impregnating pitch comprising watergas-tar pitch melting between50 and 80 C., to which has been added phenolic tar-acid, forimpregnating relatively inflexible prefabricated cellulosic fibrousmaterial such as conduit.

IRA H. DERBY.

